U.S. patent number 4,871,901 [Application Number 06/878,353] was granted by the patent office on 1989-10-03 for control device for a coffee roaster.
This patent grant is currently assigned to Sanden Corporation. Invention is credited to Takashi Chiba, Masaru Igusa.
United States Patent |
4,871,901 |
Igusa , et al. |
October 3, 1989 |
Control device for a coffee roaster
Abstract
A coffee roasting apparatus is disclosed. The coffee roasting
apparatus comprises a cylindrical container, a cylindrical drum
rotatably extended within the center portion of the container, and
a heater element diposed within the drum. The apparatus includes a
blower device to cause air circulation within the interior of the
container to more uniformily heat the beans. The heater element is
controlled by a control device to reduce the calorific value of the
heater element when the temperature of the container reaches a
predetermined temperature. Therefore, abnormal temperature in the
container is prevented, while the roasting operation is speedily
done. A control device for the blower device is also disclosed
which will vary the speed of the blower in response to changes in
the input voltage. In this way, an increase in the input voltage
which may have caused unwanted overheating is avioded by a
corresponding increase in air circulation.
Inventors: |
Igusa; Masaru (Takasaki,
JP), Chiba; Takashi (Iseaski, JP) |
Assignee: |
Sanden Corporation
(JP)
|
Family
ID: |
26436375 |
Appl.
No.: |
06/878,353 |
Filed: |
June 25, 1986 |
Foreign Application Priority Data
|
|
|
|
|
Jun 26, 1985 [JP] |
|
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60-95085[U] |
Dec 25, 1985 [JP] |
|
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60-202172[U] |
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Current U.S.
Class: |
219/400; 34/554;
219/492; 99/286 |
Current CPC
Class: |
A23N
12/10 (20130101); A23N 12/12 (20130101) |
Current International
Class: |
A23N
12/00 (20060101); A23N 12/10 (20060101); A23N
12/12 (20060101); F26B 011/04 () |
Field of
Search: |
;219/400,412,413,385,391,482,488,490,492 ;34/57O,57E,48 ;355/77
;99/286 ;323/327 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pellinen; A. D.
Assistant Examiner: Fuller; Leon K.
Attorney, Agent or Firm: Banner, Birch, McKie &
Beckett
Claims
We claim:
1. A roasting apparatus for roasting coffee beans and the like
comprising:
a container to hold the material to be roasted;
a heater element to heat the material;
a power source connected to said heater element;
a blower device for circulating air within said container;
first controlling means for controlling the calorific value of said
heater element during a roasting cycle to reduce the calorific
value from a first positive value to a second positive value when
the temperature within said container reaches a predetermined
temperature; and
second controlling means for controlling the rate at which said
blower device circulates air within said container, said second
controlling means increasing the rate at which air is circulated by
said blower device in response to an increase in the value of said
power source, and decreasing the rate at which air is circulated by
said blower device in response to a decrease in said power
source.
2. A roasting apparatus according to claim 1 wherein said first
controlling means comprises a first resistor element of a first
value, a second resistor element of a second value different than
said first value and connecting means for connecting either said
first resistor element or said second resistor element in series
with said heater element such that the voltage applied to said
heater element varies depending upon which of said resistors is
connected by said first connecting means.
3. A roasting apparatus according to claim 2 wherein said first
controlling means further comprises a condensor connected in series
with said first and second resistor elements, an alternating
switching element connected in parallel across said condensor and
said resistor elements and a trigger device connected between said
condensor and said switching element such that said condensor will
discharge during certain intervals and cause said trigger device to
activate said alternating switching element which will produce a
zero voltage level across said series combination of said resistor
and said condensor to thereby increase the voltage across the
heater element.
4. A roasting apparatus according to claim 3 wherein the time
interval during which said condensor is discharging will vary
depending upon which of said resistor elements is connected to said
heater element.
5. A roasting device according to claim 2 wherein said connecting
means is controlled by a timer device.
6. A roasting device according to claim 2 wherein said connecting
means is controlled by a thermosensor disposed in the interior of
said container.
7. A roasting device according to claim 2 wherein said connecting
means is a switch.
8. A roasting apparatus for roasting coffee beans and the like
comprising:
a container to hold the material to be roasted;
a heater element to heat the material;
a power source connected to said heater element;
a blower device for circulating air within said container; and
controlling means for controlling the rate at which said blower
device operates to thereby control the rate at which air circulates
within said container, said controlling means increasing the rate
at which air is circulated by said blower device in response to an
increase in said power source, and decreasing the rate at which air
is circulated by said blower device in response to a decrease in
said power source.
9. A roasting apparatus according to claim 8 wherein said blower
device comprises a blower fan and a motor connected to said
fan.
10. A roasting device according to claim 9 wherein said controlling
means varies the speed of said motor.
11. A roasting device apparatus for roasting coffee beans and the
like comprising:
a container to hold the material to be roasted;
a heater element to heat the material;
a power source connected to said heater element;
a blower device for circulating air within said container;
first controlling means for controlling the calorific value of said
heater element to reduce the calorific value from a first positive
value to a second positive value when the temperature within said
container reaches a predetermined temperature;
said first controlling means comprising a first resistor element of
a first value, a second resistor element of a second value
different than said first value and connecting means for connecting
either said first resistor element or said second resistor element
in series with said heater element such that the voltage applied to
said heater element varies depending upon which of said resistors
is connected by said connecting means, and further comprising
a condensor connected in series with said first and second resistor
elements, an alternating switching element connected in parallel
across said condensor and said resistor elements and a trigger
device connected between said condensor and said switching element
such that said condensor will discharge during certain intervals
and cause said trigger device to activate said alternating
switching element which will produce a zero voltage level across
said series combination of said resistor and said condensor to
thereby increase the voltage across the heater element; and
second controlling means for controlling the rate at which said
blower device circulates air within said container,
said second controlling means increasing the rate at which air is
circulated by said blower device in response to an increase in the
value of said power source, and decreasing the rate at which air is
circulated by said blower device in response to a decrease in said
power source.
12. A roasting apparatus according to claim 11 wherein the time
interval during which said condensor is discharging will vary
depending upon which of said resistor elements is connected to said
heater element.
13. A roasting device according to claim 11 wherein said connecting
means is controlled by a timer device.
14. A roasting device according to claim 11 wherein said connecting
means is controlled by a thermosensor disposed in the interior of
said container.
15. A roasting device according to claim 11 wherein said connecting
means is a switch.
Description
BACKGROUND OF THE INVENTION
This invention relates to a coffee roaster, and more particularly,
to a control device for controlling the roasting temperature of a
coffee roaster.
There are two common methods of roasting coffee, a hot blast method
and a heat radiation method. When using either method, the coffee
beans should be roasted within a very short time period to produce
high quality coffee beans. Therefore, coffee roasters use heater
elements with large calorific values for quickly roasting the
coffee beans. However, since coffee roasters are not provided with
a device for controlling the calorific value of the heater element,
the temperature in the roaster may abnormally increase and the
outer skin of the coffee bean may burn.
Some roasters are equipped with devices for more uniformly roasting
the coffee beans, for example, a stirring element or a blower
device to control the flow of air into the roaster. Thus, heat is
more uniformly distributed to each coffee bean due to the stirring
of the beans and air circulation caused by the blower element.
However, the calorific value of the heater element proportionally
changes in accordance with changes in the power source voltage so
that the amount of heat absorbed by each coffee bean within a
predetermined time period may change. As a result of variations in
the heating of the beans, the roasting condition changes thereby
making it difficult to control the degree to which each bean is
roasted.
SUMMARY OF THE INVENTION
The primary object of the invention is to provide an improved
coffee roaster in which the roasting degree of the beans can be
accurately controlled.
Another object of the invention to provide a coffee roaster with a
heater element that can be automatically controlled.
A further object of the invention is to provide a coffee roaster
with a heater element that is not affected by variations in the
power supply.
A further object of the invention is to provide a coffee roaster
with a blower device that can be controlled to vary the rate at
which air is circulated within the device.
A still further object of the invention is to provide a coffee
roaster which is protected from damage due to abnormal increases in
the temperature of the roaster.
A coffee roasting apparatus in accordance with the present
invention includes a cylindrical container which contains the
coffee beans during a roasting operation, a heater element to heat
the coffee beans, and a blower fan device to control air
circulation within the container. The calorific value of the heater
element is controlled by a control device so that the calorific
value of the heater element may be reduced when the temperature in
the container reaches a predetermined temperature. The speed of the
blower device is also adjusted to more accurately control the
roasting operation.
Further objects, features and other aspects of the invention will
be understood from the following detailed description of a
preferred embodiment of the invention with reference to the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view illustrating a roasting apparatus
according to the present invention.
FIG. 2 is an electrical circuit depicting a heater element control
device in accordance with one embodiment of the invention.
FIG. 3 is a graph illustrating the operation of the control device
shown in FIG. 2.
FIG. 4 is a graph illustrating the temperature in the roaster.
FIG. 5 is a block diagram of a control device in accordance with
another embodiment of this invention.
FIG. 6 is a graph illustrating the relationship between output
signal or rotation frequency and power source voltage.
FIG. 7 is a graph illustrating the relationship between the
calorific value and blast volume against power source voltage.
DETAILED DESCRIPTION
Referring to FIG. 1, a coffee roasting device in accordance with
the present invention is shown. The roasting device 10 comprises a
cylindrical container 11 functioning as a roasting drum, a support
frame 12 and a cylindrical drum 13 in which a heater element 14 is
disposed.
Cylindrical container 11 is formed of a transparent material with
heat resisting characteristics, for example, a glass material, and
both end openings of the container 11 are covered by end plates
121, 122 of support frame 12, respectively. Cylindrical drum 13 is
formed of a porous material such as a wire mesh and horizontally
extends within the center portion of cylindrical container 11 and
penetrates through each of end plates 121, 122. A plurality of
blades 133 project radially outward from the outer peripheral
surface of drum 13 and abut close to the inner peripheral surface
of container 11. Both end openings of drum 13 are covered by closed
plates 131, 132, each of which is rotatably supported on a fixed
shaft 15a, 15b through bearings 16a, 16b. Each fixed shaft 15a, 15b
is fixedly supported on a supporting frame 17a, 17b, each of which
is fastened on the surface of end plate 121, 122, respectively.
Heater element 14 is disposed between fixed shafts 15a, 15b. An
axial flange 132a is formed on the end portion of end plate 132 and
extends along fixed shaft 15b. A sprocket 21 is fastened on the
outer end portion of flange 132a, and is operatively connected with
a sprocket 18 fastened on the drive shaft of a driving motor 19
through endless chain 20. Thus, drum 13 is rotatably disposed
within container 11.
Coffee beans enter the container through a hole 121a which is
formed through end plate 121 and also functions as a hot air outlet
hole. A coffee bean discharge hole 121b, also formed on end plate
121, is opened and closed by control plate 22 rotatably fastened on
end plate 121. Thus, the roasted coffee beans are discharged from
container 11 through hole 121b. An air inlet hole 122a is formed
through end plate 122. A blower duct (not shown) in which a blower
fan may be disposed can be connected with air inlet hole 122a for
promoting the circulation of hot air within container 11.
Referring to FIG. 2, a control device for the heater element will
be described. One end of heater element 14 is connected to a
standard alternating power source 30 through a main switch 31, and
the other end is connected to a pair of parallely connected
resistors 32, 33 through a single pole double throw type selecting
switch 34. One of the resistors, such as first resistor 32, has a
resistance that will provide the normal input voltage for heater
element 14 when this resistor is connected by means of switch 34.
The second resistor element 33 is designed to have a resistance
larger than that of the first resistor element 32. The other end of
each of the resistor elements 32, 33 is connected to a condensor 36
which will discharge when its electrical potential exceeds a
predetermined level. The other end of each of resistor elements 32,
33 is also connected to a trigger element 37, such as an SBS, which
will generate trigger pulses by the discharge of condensor 36.
The end of heat element 14 connected to switch 34 is also connected
to alternating switching element 38 which is energized when trigger
pulses are input and is deenergized when the electric potential of
the alternating voltage wave is zero. Switch 34 is normally
connected between heater element 14 and resistor 32. Switch 34
switches to resistor 33 under the control of timer 35. In this
embodiment, timer 35 actuates switch 34 after a predetermined time
period, for example, ten minutes after the closing of main switch
31.
When the roasting operation is begun, motor 18 for rotating
cylindrical drum 13, and heater element 14 is energized. After the
temperature in the roasting drum reaches a predetermined
temperature, coffee beans are placed in the interior of cylindrical
container 11 through hole 121a. The coffee beans are uniformly
heated by heater element 14 due to the rotating operation of blades
133. After the roasting operation is completed, the rotating
operation of motor 18 is ceased, heater element 14 is deenergized,
and roasted coffee beans are discharged through hole 121b.
Referring to FIG. 3, the operation of timer 35 and trigger element
36 will be explained. When switch 31 is first closed, switch 34 is
connected to resistor 32. Since the resistance of first resistor
element 32 is small, the electrical potential of condenser 36
quickly reaches a predetermined level, such as the trigger level of
the trigger element (this change of potential of the condensor is
shown by curve A in FIG. 3(b), while the voltage of the power
source is shown in FIG. 3(a)). After the trigger level is reached,
condensor 36 begins to discharge into trigger element 37, and is
fully discharged when the voltage of the alternating current source
reaches the zero level. The trigger pulse which is generated by the
trigger element 37 and shown by curve A' in FIG. 3(c) is input to
alternating switching element 38 which will close and result in a
large input voltage being supplied to heater element 14. As a
result, the calorific value of heater element 14 is high.
After a predetermined time period, such as ten minutes from the
closing of main switch 31, switch 34 is activated due to the
operation of timer 35 and is now connected to resistor 33. Since
the resistance of resistor 33 is larger than that of resistor 32,
the electrical potential of condensor 36 is gradually increased to
the trigger level of trigger element 37 (this change of potential
of condenser 36 is shown by curve B in FIG. 3(b)). The charging
time to reach the trigger level is now delayed, as shown in FIG.
3(b). After the trigger level is reached condensor 36 discharges,
and is completely discharged when the alternating voltage curve
reaches zero. The trigger pulse which is generated by the trigger
element 37 and shown by curve B' in FIG. 3(d) is applied to
switching element 38. Thus, the large input voltage supplied to
heater element 14 is supplied for a shorter time due to second
resistor 33. As a result, the calorific value of heater element 14
is varied.
In this embodiment, switch 34 is controlled by the operation of
timer 35, however, switch 34 could be controlled by a detecting
signal from a thermosensor 24 disposed in the interior of
cylindircal container 11 (see FIG. 1).
As mentioned above, the calorific value of the heater element is
controlled by a change of input voltage to the heater element, and
is maintained at a high level at the initial stage of the roasting
operation so that the temperature in the cylindrical container
quickly reaches an appropriate roasting temperature T1 and the
coffee beans are roasted by high heat during a short time period.
After the temperature in the cylinder container reaches the
appropriate roasting temperature level T1, the calorific value of
the heater element is reduced. Thereafter, the temperature in the
cylinder container is slowly increased to thereby prevent abnormal
heating within the cylinder container. That is, as shown in FIG. 4,
the time period to reach the temperature level T2 from temperature
level T1 is longer than in prior devices. As a result, burning of
the skin of the coffee beans is prevented. As shown in FIG. 4(b),
the calorific value of the heater element is reduced after the
predetermined time period. Precise temperature control in the
cylindrical container is further accomplished by controlling the
operation of the blower fan.
Referring to FIG. 5, the operation of a blower motor will be
described. The blower motor operates a blower fan which is disposed
in the blower duct and causes hot air circulation within the
cylindrical container to more uniformly roast the coffee beans and
control the temperature in the container. The rotation speed of the
blower is controlled by air flow control circuit 40.
Control circuit 40 comprises a rotation frequency detecting sensor
41, F-V transfer circuit 42 by which the rotation frequency or
frequency signal is transferred to a direct current signal, a
reference voltage generating circuit 43, a differential amplify
circuit 44 and a speed control circuit 45 to which blower motor 231
is connected. The rotation frequency detecting sensor 41 is
disposed on the outer peripheral portion of the blower fan 23 to
detect the rotation frequency of the blower fan 23, and its
detecting signal is input to F-V transfer circuit 42. The direct
current signal generated by F-V transfer circuit 42 is input to
speed control circuit 45.
Differential amplify circuit 44 is connected in parallel to
alternating power source 30 and heater element 14, and is also
connected to reference voltage generating circuit 43. This
differential amplify circuit 44 detects the difference between the
two voltages applied from alternating power source 30 and reference
voltage generating circuit 43, and amplifies this difference. The
amplified signal generated by difference amplify circuit 44 is
input to speed control circuit 45. Speed control circuit 45
controls the rotation frequency of blower motor 231 in response to
the signal input thereto.
The operation of the speed control circuit 45 will be explained
with reference to FIGS. 6 and 7. The rotation frequency of blower
fan 23 is detected by the rotation frequency detecting sensor 41
and is input to F-V transfer circuit 42.
This rotation frequency signal is transferred to a direct current
signal and input to speed control circuit 45.
If the power source voltage applied to heater element 14 exceeds
the reference voltage generated by the reference voltage generating
circuit 43, i.e., the calorific value of heater element 14 is
proportionally increased due to an increase in the power source
voltage, the differential amplify circuit 44 amplifies the voltage
difference between these two voltages and inputs the difference
voltage signal to speed control circuit 45. The rotation speed of
blower motor 231 is proportional to the voltage supplied by
differential amplify circuit 44 and is, therefore, varied in
accordance with changes in the power supply 30. In speed control
circuit 45, the input signal from F-V transfer circuit 42 is
compared with the input signal from differential amplify circuit
44, and then a signal is outputted to control the rotation speed of
blower motor 231. Thus, the rotation frequency of blower motor 231
proportionally increases when the voltage of the power source
increases.
The relationship between the rotation frequency, airflow amount and
waste heat volume are proportional to one another, thus, the waste
heat volume is proportionately increased when the voltage of power
source 30 is increased, as shown by the dotted line in FIG. 7.
Therefore, even if the calorific value of the heater element is
increased due to increases in the voltage of the power source, the
waste heat volume is proportionately increased due to the
increasing of the rotation frequency of blower motor 231. As a
result, the heating value Q supplied to the roasted coffee bean is
usually constant, as shown in FIG. 7. Reversely, if the heating
value of heater element 14 is decreased, the waste heat value by
the operation of blower motor 231 is proportionately decreased.
As mentioned above, the heater element control device is provided
with a rotation speed control circuit for controlling the rotation
frequency of the blower motor in order to compensate for changes of
voltage in the power source. The heating value supplied to the
coffee beans is therefore usually constant and optimum roasting
conditions are maintained.
This invention has been described in connection with the preferred
embodiments, but these embodiments are for illustrative purposes
only, and the invention should not be construed as limited thereto.
Although the control devices described herein have been illustrated
in the environment of a coffee roaster, it should be apparent that
the controlling apparatus could be used to control any heating or
roasting device. It should be apparent to those skilled in the art
that other variations or modifications can be made without
departing from the spirit of the invention or the scope of the
appended claims.
* * * * *